Implementation of Ramanujan's Taxi by Srinivasa Ramanujan in three different optimizations. Find details at: https://medium.freecodecamp.com/the-man-who-knew-infinity-coding-ramanujans-taxi-52e4c3696e53#.lyvjdqpq2
G.H. Hardy: "I remember once going to see him when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavorable omen. "No," he replied, "it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways." https://en.wikipedia.org/wiki/1729_(number)
The algorithms are implemented in O(n^4), O(n^3), and O(n^2).
Formula: a^3 + b^3 = c^3 + d^3
Where: a^3 <= n; b^3 <= n; c^3 <= n; d^3 <= n; a != c & a != d; b != c & b != d